We have seen where Warren left Antigua on March 13th in his flag ship, Superbe, a large man-of-war (60 guns) in company with the Mermaid (40 guns) and the Launceston (40 guns). They were to arrive off Canso on April 23rd. Just at that time they were joined by a fourth, Eltham (44 guns) which had come up from Boston.1 They did not spend any time at Canso but were to proceed, all four, a further way up the coast so as to blockade Louisbourg. (See map 1 and map 2.)

So, initially we see Warren with four British men-of-war standing off the mouth of Louisbourg Harbour.3 With such a number to be effective they would have to keep sailing and stand in fairly close to the shores surrounding the mouth of Louisbourg Harbour; so close, that on occasion the French gunners were tempted to get in a shot at them.4 Rarely did these vessels go into Gabarus Bay, the handiest anchorage outside of Louisbourg Harbour. They would constantly have been sailing back and forth, no matter the weather5 or sea condition; for a blockade was only effective if they were to keep it up. If a sail showed up on the horizon, in concert with the other blockading vessels, and ever mindful of keeping a continual cover on the mouth of the harbour, they would chase it down. This business would require the involvement of all available vessels; yet, we see where on May the seventh, or thereabouts, the Eltham was detached and sent over the top end of Cape Breton Island (See map, from #15 to #17) to get at the settlement at St. Ann's (Port Dauphin), there "to burn and destroy what they could of the enemy."6 Because of the limited number in Warren's fleet, and, because, it was not entirely devoted to the blockade, Warren, while achieving considerable success, did not shut down Louisbourg's harbour entirely. We see, that on May 13th, "A French snow from Bordeaux got in ..."7 Warren wrote of this:

Warren Takes the Vigilant
The role of Warren's fleet at Louisbourg, therefore, was to lock up Louisbourg's harbour. Its job, in this regard, was to be made easier and indeed the role was to change with the addition of more men-of-war. New arrivals, and a capture, as we shall see, were to eventually put eleven British war ships off Louisbourg though not all of them were in place until the first of June. These very impressive men-of-war carried near as many men as were on shore: "3,585 officers, seamen, and marines." And, much more in the way of firepower: 554 naval cannon.9

That on the 18th ult. the Mermaid, Capt. Douglas, a 40 gun ship, and the Shirley-Galley, Capt. Rouse, one of our cruizers, fell in with a French Man of War, and engaged her, the former broadside and broadside; and the latter being too small to lay along-side, and going well, annoyed her astern, or ahead, or on the quarter, as he could best; and as she proved a ship of force, they knowing how the Commodore got along side near enough to engage, when after 2 or 3 broadsides, she struck and asked for quarters, and was the next day secured; she is called the Vigilant, a new ship never at sea before, of 64 guns, and 560 men, and was commanded by the Marquis du Maisonfort ..."14

Seth Pomeroy, witnessing the event from the shore observed that the battle, "yard arm to yard arm," took place over a period of two hours. "The Suberbe, the Mermaid, Eltham, Massachusetts Frigate and Shirley Galley were all in the engagement and at the taking of her ..."15 At such odds, it is a wonder that the Vigilant fought on for better than two hours. Pomeroy reported that the British lost four men and the French, 30 and many more wounded.16

The Vigilant was a handsome dividend21 and all of those comprising of Warren's squadron must have been indeed very pleased with themselves; but the capture of the Vigilant, as valuable as she was in British hands, paid a larger dividend, viz., the eventual delivery of Louisbourg. Had the Vigilant gotten in it's doubtful whether Louisbourg would have been taken that season.22 And, so, like manna from heaven, valuable military stores fell into the hands of the English. The most valuable and most needed of the supplies aboard the Vigilant was that of the gun powder: one thousand barrels of it. As well, taken off of her and added to the British stores, were twenty bronze cannons, these, together with the other captured provisions, if they had been delivered, might will have extended Louisbourg's French life for a further four months after which time the invaders, in the face of winter, would have had to retire from the field. The capture of the Vigilant also denied the Louisbourg garrison the reinforcement of three hundred soldiers which were aboard the Vigilant.23

So it was, on June 12th, 1745, Commodore Peter Warren "commanded the largest British squadron in North American waters since 1711": Eleven men-of-war, including the captured Vigilant.26 With such forces at his command, Warren was chafing at the bit. All that was necessary was to get close enough to Louisbourg so as to employ his more than 500 naval cannon. But that could come about, only if he could make his way into Louisbourg Harbour; and for that, his fleet would have to sail by in close range to the Island Battery, and, in so doing, suffer from the point blank punishment meted out by crack French crews who were manning well fortified and stationary gun emplacements; and who, were at the ready.